In this paper, the natural convection in a square enclosure, partly heated from below, with two adiabatic vertical wall and one upper horigental wall is studied nomerically. In numerical study, SIMPLE(Semi-Implicit for Pressure Linked Equation) algorithems are applied for the integration of momentum and energy equation. The grid size used in this study is the coordinates of size (22$ imes$22). As a result of numerical analysis, the initial fluid flow depends on the thermal diffusion, but, as time passes, the fluid flow depends on convection and buoyancy of the enclosure. In Case 1, the heating region was been in the central position of the bottom wall. In case 2, the heating region was in the left position of the bottom. In case of Case 1, the lapse time of sensing the temperature of 72$^{circ}C$ is approximately 15 sec almost at the same time in the coordinates (6, 22), (11, 22). In case of Case 2, the lapse time in the coordinates (6, 22), (11, 22) was 27 sec, 25 sec repectively. Also in case of Case 1 or Case 2, the gradients of y-position of the two sensors are transposed each other.